This invention relates to the processing of a pixel-based image for the purpose of predicting whether that image, when used as a repeat unit in a pattern and viewed over a large number of pattern repeats, will exhibit unintended and undesirable pattern artifacts. In another embodiment, this invention may be used to modify a pattern for the purpose of reducing or minimizing the visual perceptibility of such pattern artifacts.
More particularly, this invention relates to a method for analyzing a small portion of a repeating pattern--one containing at least one complete pattern repeat--and predicting whether concentrations of pattern elements or colors within that single pattern repeat collectively will form an undesirable large scale pattern when a large number of pattern repeats are viewed, particularly at a relatively shallow viewing angle. This invention is also useful in generating a modified pattern repeat in which such unintended pattern artifacts are made less visually obtrusive. Accordingly, the techniques disclosed herein can serve as a tool both to identify and correct such patterns, without the need for physically fabricating a patterned substrate having a large number of pattern repeats, making observations of the substrate at a relatively shallow viewing angle, and repeating the fabrication and observation process until a suitable substrate pattern is developed.
This method is particularly suited, but is not limited to, detecting such patterns and associated undesirable pattern artifacts in floor coverings that, in use, commonly are viewed at a relatively shallow sight angle that includes a relatively large number of pattern repeats. Although the description herein shall refer to carpet patterns, the technique is also applicable to patterns associated with drapery fabric, home or automotive upholstery, wall coverings, or any other patterned materials, objects, or media that are patterned using a relatively large number of pattern repeats or that are viewed at a relatively shallow sight angle, or both.
Designers of patterned substrates recognize the fact that patterns have both a small-scale and a large-scale character. A pattern that presents a visually acceptable image when viewed over one or a few pattern repeats can, if viewed over many pattern repeats, exhibit an objectionable large-scale pattern such as "banding" or "blobbing" (as those terms are defined hereinbelow) that is extremely difficult to detect or predict when only one or a few pattern repeats are observed. Furthermore, some patterns, when viewed at a relatively low sight angle (as naturally occurs with patterned floor coverings in large rooms), can exhibit additional or accentuated unintended patterning due to the ability of the eye to integrate visually otherwise unobtrusive patterning features along a shallow line of sight. This generally well-known phenomenon shall be referred to herein as visual integration. As used herein, the term "visually integrated pattern" or "large scale patterning artifact" shall be used interchangeably to describe the unintended pattern that is formed when several individually identical pattern repeats are viewed together, and that is best perceived when a large number of individual pattern repeats are viewed at one time and at a relatively shallow viewing angle, as, for example, a carpet pattern as viewed after the carpet is installed on the floor of a large room. As used herein, the term "component pattern" shall be used to describe the individual pattern elements or individual pattern repeats that, when replicated or tiled, form the overall patterned surface.
The terms "banding" and "blobbing" shall refer to a concentration of color or pattern elements, usually undesirable, that is most visually apparent when the pattern is viewed over multiple pattern repeats, at a shallow sight angle (thereby enhancing the visual integration effect), or both. In banding, the concentration takes the form of one or more visually perceptible bands or ribbons of color or shading that run through a series of pattern repeats and tend to distract the eye from the intended pattern; in blobbing, the concentration is in the form of one or more islands of color or pattern that appear to stand out from the background in a way that is not visually apparent when viewing one or a small number of pattern repeats in isolation, and that tend to detract from the intended patterning effect. The term "tile" or "tiled" shall be used in a mathematical sense, i.e., the placement of individual pattern repeats in abutting relationship so as to form a continuous, uninterrupted pattern, with common boundaries and no gaps between adjacent pattern repeats.
A major problem for carpet designers has been to determine, prior to undertaking the expense of manufacturing a sufficiently large sample of the patterned carpet and viewing that sample on the floor under various lighting conditions, which patterns are prone to large scale patterning artifacts such as banding or blobbing. As a secondary problem, designers frequently have had to use an educated trial-and-error approach to determine the best way to minimize or eliminate such artifacts once discovered. The cathode ray tube (CRT) video monitors that are commonly used by carpet designers in computer-aided design processes generally have inadequate resolution to allow the representation of a large enough number of pattern repeats, each with sufficient detail, to allow a meaningful visual evaluation of a given pattern. Additionally, such monitors are frequently subject to moire, "dot crawl" and other electronic artifacts associated with CRT imaging that make the fine detail frequently necessary to simulate such patterning artifacts difficult to image accurately. If fine pattern detail cannot be imaged accurately, then generating a sufficient number of pattern repeats necessary to see large scale patterning artifacts tends to distort or remove pattern information from the resulting image, and jeopardizes the ability to predict with confidence the presence of these artifacts.
The invention described herein presents a solution to this problem by allowing a computer-based designer of, for example, carpets, to (1) evaluate candidate carpet patterns and reliably identify those most likely to produce unintended large scale patterning artifacts, and (2) develop modifications to those patterns that reduce the indicated artifacts, and to do either without having to fabricate a large number of carpet samples and place them on a floor for evaluation. The techniques disclosed herein essentially exaggerate large scale patterning artifacts that tend to become more visually noticeable as the number of pattern repeats increases or the viewing angle decreases, or both, and can generate an "inverse" of the troublesome pattern areas that, when combined with the original pattern, can reduce or eliminate such artifacts.